Methods of making paper tissue, towel, and the like are well known, including various features such as Yankee drying, throughdrying, fabric creping, dry creping, wet creping and so forth. Conventional wet pressing/dry creping processes (CWP) have certain advantages over conventional through-air drying processes, including: (1) lower energy costs associated with the mechanical removal of water rather than transpiration drying with hot air; and (2) higher production speeds which are more readily achieved with processes which utilize wet pressing to form a web. On the other hand, through-air drying processing has been widely adopted for new capital investment, particularly for the production of soft, bulky, premium quality towel products.
Throughdried, creped (TAD) products and processes are disclosed in the following patents: U.S. Pat. No. 3,994,771 to Morgan, Jr. et al.; U.S. Pat. No. 4,102,737 to Morton; and U.S. Pat. No. 4,529,480 to Trokhan. The processes described in these patents comprise, very generally, forming a web on a foraminous support, thermally pre-drying the web, applying the web to a Yankee dryer with a nip defined, in part, by an impression fabric, and creping the product from the Yankee dryer. A relatively permeable web is typically required, making it difficult to employ recycle furnish at levels which may be desired. Transfer to the Yankee typically takes place at web consistencies of from about 60% to about 70%. See also, U.S. Pat. No. 6,187,137 to Druecke et al. which includes disclosure of peeling a web from a Yankee dryer. As noted in the above, throughdried products tend to exhibit enhanced bulk and softness; however, thermal dewatering with hot air tends to be energy intensive. Wet-press, dry crepe operations, wherein the webs are mechanically dewatered, are preferable from an energy perspective and are more readily applied to furnishes containing recycle fiber, which in many cases tends to form webs with less permeability than virgin fiber. Moreover, line speeds tend to be higher with wet-press operations.
A wet web may also be dried or initially dewatered by thermal means by way of impingement air drying. Suitable rotary impingement air drying equipment is described in U.S. Pat. No. 6,432,267 to Watson and U.S. Pat. No. 6,447,640 to Watson et al.
Fabric creping has been employed in connection with papermaking processes which include mechanical or compactive dewatering of the paper web as a means to influence product properties. See U.S. Pat. Nos. 4,689,119 and 4,551,199 of Weldon; 4,849,054 and 4,834,838 of Klowak; and 6,287,426 of Edwards et al. Operation of fabric creping processes has been hampered by the difficulty of effectively transferring a web of high or intermediate consistency to a dryer. Note also U.S. Pat. No. 6,350,349 to Hermans et al. which discloses wet transfer of a web from a rotating transfer surface to a fabric. Further United States patents relating to fabric creping more generally include the following: U.S. Pat. Nos. 4,834,838; 4,482,429; 4,445,638, as well as 4,440,597 to Wells et al. Newer processes including fabric-creping are described in: U.S. application Ser. No. 10/679,862, entitled “Fabric Crepe Process for Making Absorbent Sheet” which application, incorporated herein by reference, discloses particular papermachine details as well as creping techniques, equipment and properties.
Other processes for making heavyweight premium paper for absorbent sheet include air-laid (AL) processes and double-crepe (DRC) processes. These processes utilize polymeric binder for strength which makes the product difficult to recycle; and, in any event, these processes are expensive to install and operate. AL and DRC are used in single ply finished products.
While technology for making absorbent disposable paper products is highly sophisticated, it is typical to “trade” one attribute for another. For example, strength increases are achieved at the expense of other properties such as stiffness (modulus increase) which may be undesirable in a product such as a premium paper towel.